ci: Add dist-aarch64-freebsd

Add scripts to build the aarch64-unknown-freebsd target in CI.
Implements MCP: rust-lang/compiler-team#961

Author: mrkajetanp

src/ci/docker/host-aarch64/dist-aarch64-freebsd/Dockerfile

@@ -0,0 +1,46 @@
+FROM ubuntu:22.04
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+  clang \
+  make \
+  ninja-build \
+  file \
+  curl \
+  ca-certificates \
+  python3 \
+  git \
+  cmake \
+  sudo \
+  bzip2 \
+  xz-utils \
+  texinfo \
+  wget \
+  libssl-dev \
+  pkg-config \
+  && rm -rf /var/lib/apt/lists/*
+
+COPY scripts/freebsd-toolchain.sh /tmp/
+RUN /tmp/freebsd-toolchain.sh aarch64
+
+COPY scripts/sccache.sh /scripts/
+RUN sh /scripts/sccache.sh
+
+COPY scripts/cmake.sh /scripts/
+RUN /scripts/cmake.sh
+
+ENV \
+    AR_aarch64_unknown_freebsd=aarch64-unknown-freebsd13-ar \
+    CC_aarch64_unknown_freebsd=aarch64-unknown-freebsd13-clang \
+    CXX_aarch64_unknown_freebsd=aarch64-unknown-freebsd13-clang++
+
+ENV HOSTS=aarch64-unknown-freebsd
+
+ENV RUST_CONFIGURE_ARGS \
+    --enable-full-tools \
+    --enable-extended \
+    --enable-profiler \
+    --enable-sanitizers \
+    --disable-docs
+
+ENV SCRIPT python3 ../x.py dist --host $HOSTS --target $HOSTS
+

src/ci/docker/scripts/freebsd-toolchain.sh

@@ -5,8 +5,16 @@ set -eux
 
 arch=$1
 binutils_version=2.40
-freebsd_version=12.3
-triple=$arch-unknown-freebsd12
+case $arch in
+    (aarch64)
+        freebsd_version=13.5
+        triple=$arch-unknown-freebsd13
+        ;;
+    (*)
+        freebsd_version=12.3
+        triple=$arch-unknown-freebsd12
+        ;;
+esac
 sysroot=/usr/local/$triple
 
 hide_output() {
@@ -45,6 +53,7 @@ mkdir -p "$sysroot"
 case $arch in
   (x86_64) freebsd_arch=amd64 ;;
   (i686) freebsd_arch=i386 ;;
+  (aarch64) freebsd_arch=arm64 ;;
 esac
 
 files_to_extract=(
@@ -61,7 +70,15 @@ done
 
 # Originally downloaded from:
 # URL=https://download.freebsd.org/ftp/releases/${freebsd_arch}/${freebsd_version}-RELEASE/base.txz
-URL=https://ci-mirrors.rust-lang.org/rustc/2022-05-06-freebsd-${freebsd_version}-${freebsd_arch}-base.txz
+# FIXME: Switch to fully using the mirror once arm64 is available there
+case $arch in
+    (aarch64)
+        URL=https://download.freebsd.org/ftp/releases/${freebsd_arch}/${freebsd_version}-RELEASE/base.txz
+        ;;
+    (*)
+        URL=https://ci-mirrors.rust-lang.org/rustc/2022-05-06-freebsd-${freebsd_version}-${freebsd_arch}-base.txz
+        ;;
+esac
 curl "$URL" | tar xJf - -C "$sysroot" --wildcards "${files_to_extract[@]}"
 
 # Clang can do cross-builds out of the box, if we give it the right